1. Field of the Invention
The present invention relates to an improvement in the formability and mechanical properties of aluminum-lithium alloys.
2. Prior Art
Lithium, the lightest metal occurring in nature has been alloyed with aluminum to reduce the density thereof. Aluminum-lithium alloys are highly coveted for applications requiring high strength, high elastic modulus and low density such as in the aerospace industry. [Mehrabian et al, Rapid Solidification Processing Principles and Technology II, Claitor's Pub. Div. (1980)]. The alloys have not found wide commercial acceptance, however, in view of their unacceptable ductility, fracture toughness and notch sensitivity values and the concomitant difficulty of fabrication of articles therefrom. These poor properties have been attributed to the use of .delta.' phase alloys produced by the conventional precipitation hardening mechanism within the .delta.' solvus. [Sanders et al, Aluminum-Lithium Alloys, Proc. 1st. Int. Al-Li Conf., Stone Mountain, Ga., TMS-AIME, (1980)].
It is an object of the present invention to provide a method of strengthening which greatly improves the ductility, formability and other mechanical properties of aluminum-lithium alloys.